The present invention is directed to a hydrogen-fueled gas fireplace, and in particular a gas fireplace fueled by hydrogen generated by a small electrolyzer.
Gas fireplaces are commonplace in many homes today. They are able to provide the advantages of real wood burning fireplaces without any of the disadvantages such as the hauling of wood logs and the clean up of soot. To produce flames, the fireplaces are equipped with one oraplurality of burners. Each burner typically has a gas inlet and a plurality of outlet ports. Gas enters the burner through the gas inlet. The gas is ignited as it exits the outlet ports. Traditional gas fireplaces burn gases such as natural, which results in the production of undesirable emissions such a carbon monoxide, unburned hydrocarbons and nitrous oxide. Thus, a need exists for a gas fireplace that does not produce emissions, for example, by burning hydrogen.
The production of hydrogen using an electrolyzer is not new, but has previously been limited to industrial size applications, which involve large numbers of cells (typically 150) in series, in order to build up the overall voltage (at approximately 2 volts per cell) to the necessary voltage. There are two general types of electrolyzers. unipolar electrolyzers and filter press electrolyzers. Filter press electrolyzers have multiple cells in series such that the normal current flows from one end plate through each cell to the opposite end plate. Conventional electrolyzers have cells interconnected via an electrolyte distribution system comprising channels or ducts at the top of each cell for gas and electrolyte removal and at the bottom of each cell for electrolyte return. In other words, the electrolyte distributions systems are not individual to each cell. One of the problems associated with such traditional systems is that, in addition to the normal current flow, there are also parasitic flows through the channels or ducts that extend through adjacent cells for removal of gases and return of electrolyte supply. These parasitic flows have two negative effects. First they reduce the efficiency of the cells systems because the parasitic current flow creates heat rather than produces gas. Second, when the cells are not in use. reverse potentials may be created via the parasitic channels, giving rise to corrosion and deactivation. Thus, a need exists for a more cost-effective electrolyzer system, in particular. one that reduces parasitic current flows.
The present invention provides a novel means for generating hydrogen gas which is particularly useful in domestic applications, particularly, a hydrogen fueled gas fireplace. The hydrogen generating means comprises a filter-press electrolyzer that generates hydrogen from an electrolyte solution and has a relatively small size. e.g., about 600 mm2, and is thus convenient for domestic use. Suitable domestic applications include cooking stoves and the like as well as gas fireplaces.
In one embodiment, the hydrogen generating means comprises a filter-press electrolyzer and a switch mode power supply. The electrolyzer has a series of between about 5 and 30 cells, more preferably between about 5 and 15 cells, that are capable of producing hydrogen gas and oxygen gas from an electrolyte solution. The switch mode power supply, which converts alternating current to unidirectional current, is electrically connected to the electrolyzer. This design avoids the need for a large, inconvenient transformer to power the electrolyzer.
In a preferred embodiment, the filter-press electrolyzer comprises a series of cells capable of producing hydrogen gas and oxygen gas from an electrolyte solution. wherein each cell comprises:
(i) a cathode plate capable of generating hydrogen gas from the electrolyte solution,
(ii) an anode plate capable of generating oxygen gas from the electrolyte solution spaced apart from the cathode,
(iii) a hydrogen and oxygen gas impermeable membrane spaced between the cathode and anode,
(iv) a first gasket adjacent the periphery of the cathode between the cathode and the membrane, and
(v) a second gasket adjacent the periphery of the anode between the anode and the membrane.
Preferably, the electrolyzer further comprises a hydrogen settling tank and an oxygen settling tank. The electrolvzer further comprises means for carrying hydrogen gas generated in each cell to the hydrogen settling tank and means for carrying oxygen generated in each cell to the oxygen settling tank. Preferred hydrogen and oxygen carrying means comprise a separate hydrogen and oxygen gas passages (or ducts) that extend through the cathode plates, anode plates, gaskets and membranes of the electrolyzer to hydrogen and oxygen pipes which extend to the hydrogen and oxygen settling tanks. By utilizing separate hydrogen and oxygen flowpaths for each cell, parasitic currents are significantly reduced, particularly where the settling tanks are constructed from non-conductive materials.
In another preferred embodiment, the invention is directed to a filter-press electrolyzer comprising a series of cells as described above. Each of the cathode, anode, membrane, first gasket and second gasket contains at least one hydrogen gas hole aligned to form at least one hydrogen gas flowpath that extends through the series of cells to the hydrogen settling tank. Each of the cathode, anode, membrane, first gasket and second gasket contains at least one oxygen gas hole aligned to form at least one oxygen gas flowpath that extends through the series of cells to the oxygen settling tank. Additionally each of the cathode, anode. membrane, first gasket and second gasket contains at least one electrolyte return hole to form at least one electrolyte return flowpath that extends from the hydrogen and oxygen settling tanks to and through the series of cells to return electrolyte carried to the settling tanks by the generated hydrogen and oxygen. Preferably, the hydrogen settling tank and oxygen settling tank are immediately adjacent to the cells. This design permits the electrolyte solution to circulate within the electrolyzer without the use of a pump, which may be required if the settling tanks are not in close proximity.
In yet another preferred embodiment, the flowpaths of the electrolyzer are insulated to reduce the creation of parasitic currents. Specifically, each hydrogen gas flowpath, each oxygen gas flowpath, and each electrolyte return flowpath is lined, at least in part, and preferably completely. by an insulating material.
A particularly preferred application of the above-describe electrolyzer is a hydrogen-fueled fireplace. The fireplace comprises a firebox. a burner assembly within the firebox, and a means for generating hydrogen gas and for directing generated hydrogen gas to the burner. Burning the hydrogen gas in the firebox in the presence of oxygen produces a flame. Preferred means for generating hydrogen gas include the above-described electrolyzer designs.
Fireplaces made in accordance with the present invention are capable of producing a flame effect from water and electricity. Moreover, the fireplace produces essentially zero emissions, avoiding carbon deposition, a serious concern when burning carbon-based fuels such as natural gas. Another advantage of the present fireplace is that the hydrogen flame produces a more natural flame, creating the appearance that the flame is xe2x80x9clickingxe2x80x9d out and around the logs.
In one preferred embodiment, the fireplace comprises a first plenum fluidly connected to the inside of the firebox and extending above, behind and below the firebox. A reservoir is located at the bottom of the first plenum. Water vapor generated by burning hydrogen in the presence of oxygen condenses as it falls within the plenum behind the firebox into the reservoir to thus recycle the water vapor.
In a more preferred embodiment, the fireplace further comprises a second room air plenum located behind the first plenum and above and below the firebox. The second plenum is open above and below the firebox to room air outside of the firebox. Room air passes into the bottom portion of the second plenum, passes up through the rear portion of the second plenum behind the firebox where it is heated by the heat combustion products in the first plenum, and out through the top of the second plenum at an increased temperature. By this design, a heat-exchanger effect is created. Preferably the heated room air exiting the fireplace is directed in a generally downward direction. Thus it appears that the heat generated from the fireplace is coming directly from the fire.
The invention also provides a flashback arrestor system. The flashback arrestor system comprises a primary chamber having a top and bottom and a gas outlet therefrom and an input chamber having a top and bottom and connected to a source of gas and liquid. A passage connects the bottom of the primary chamber to the bottom of the input chamber. A porous material extends across the primary chamber in such a manner that any gas passing through the primary chamber must pass through the porous material. Gas and liquid enter the input chamber and flow into the primary chamber. The gas is broken into small, non-contacting bubbles as it passes through the porous material. The non-contacting gas bubbles flow through the liquid in the primary chamber, thereby preventing gas flashback through the primary chamber. Preferably the flashback arrestor system further comprises a non-return valve in the input chamber.
In a particularly preferred embodiment, the fireplace and electrolyzer described above are combined with the above-described flashback arrestor system. Hydrogen gas and electrolyte solution enter the input chamber from the hydrogen settling tank and flow into the primary chamber. The hydrogen gas is broken into small, non-contacting bubbles as it passes through the porous material. The non-contacting gas bubbles flow through the electrolyte in the primary chamber, thereby preventing gas flashback through the primary chamber from the burner.
The present invention also provides a self-contained power module. The power module includes an enclosure having input and output connectors. Internal to the enclosure is a first full-wave rectifier which is connected to the input connector of the enclosure. The output of the first full-wave rectifier is coupled to a chopper. The chopper has an output with a variable duty cycle. The chopped output is applied to a primary winding of a transformer. The secondary winding of the transformer is connected to a second full-wave rectifier. The output of the second full wave rectifier is connected to the output connector of the enclosure. In this embodiment, when an AC voltage is applied to the input connector, a rectified sinusoidal waveform appears at the output connector.